Hematopoietic Stem Cell (HSC) Graft Cryopreservation Effects on Outcomes of Patients with Hematologic Malignancies: the Multicenter United Kingdom Experience During the COVID-19 Pandemic.

The effects of graft cryopreservation on patient outcomes in allogeneic hematopoietic cell transplantation (HCT) remains unclear. In our multicenter UK study, outcomes of 926 adults receiving an allogeneic cryopreserved peripheral blood stem cell (PBSC) graft for a malignant hematologic indication between June 2020 and September 2021 were compared with 1491 adults with hematologic malignancy transplanted June 2018 to September 2019 with fresh PBSC grafts. There were short delays in median platelet and neutrophil engraftment with cryopreserved hematopoietic stem cell (HSC) grafts: 18 versus 15 days (P < .01) for platelets and 14 versus 13 days (P < .01) for neutrophils in the cryopreserved and fresh historical control groups, respectively. Reassuringly, primary graft failure rates were similar (P = .48). Relapse rates were higher (P = .03) but non-relapse mortality was lower (P < .01) in the cryopreserved group at 12-month follow-up. There was no statistical difference in overall survival between the groups (P = .52). Cryopreservation of allogeneic HSC grafts remains an important quality consideration in HCT practice. Advancement of our clinical and scientific understanding of this aspect of laboratory processing of HCT grafts is essential in relation not only to the pandemic but also for its use in other clinical and logistical settings where fresh donations are not feasible.